Optical touch screens are a form of light sensitive display interfaces. An optical touch screen uses light sensors to detect an object being placed in proximity or against a display interface. Many existing optical touch screen applications use a controlled environment, where incidental or inadvertent light variations are less of an issue. But there is increasing attention to using optical touch screens on portable and small-form factor devices, because optical touch screens provide better lighting, are more efficient, and can potentially reduce thickness of the device.